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Straight vs. angled aircraft carrier decks: tradeoffs for rolling takeoff?
I have some questions about modern aircraft carriers and the tradeoffs they make when choosing between straight or angled runways when used with modern jet aircraft for rolling takeoffs.
This question is not about old (e.g. WW2) aircraft carriers with straight decks nor is it about propeller planes or jet aircraft with VTOL or STOL.
So let's establish a few things first (obviously please correct me if I'm wrong on anything):
a. Angled runways allow simultaneous launching and recovery.
b. Angled runways allow aircraft to bail out and try again during recovery.
c. Angled decks have a shorter takeoff runways and shorter landing
    runways than straight decks (which can just have a single longer
    runway for both tasks).
d. As a result of (c), assistive devices for landing and takeoff (such
    as catapults) are much more critical with angled decks than straight
    decks. (FALSIFIED because carrier decks are several times shorter than required and a little extra runway length is not going to matter)
So here are my question:

Are modern non-VTOL/STOL jet aircraft still not able to take off from the single longer runway of a straight deck without catapults?
If the following image is correct, on modern straight decks, aircraft stored at the end or on the sides? Because it seems that if the aircraft were stored on the sides, although you couldn't perform simultaneous launch and recovery, you could at least switch between launch and recovery fairly quickly since you would not have to move any planes out of the way except for the one that is on the runway. You could also bail from a bad landing.

How closely does this "fast-switching" between launch and recovery compare against actual simultaneous launch and recovery?
I assume this just wasn't done on WW2 carriers because they were smaller so there was no room to store aircraft on the sides; They had to be stored at the end which meant no landings until every plane ready for takeoff was cleared.
I read that angled decks are much more expensive than straight decks. I imagine this is because angled decks require a runway extension and catapults (since planes would not be able to launch off the shorter takeoff runway of a angled deck without one), plus a nuclear reactor since you need one for a steam catapult. However, if it turns out that modern non-VTOL/STOL aircraft cannot takeoff without catapults from an straight deck, then where is this supposed cost difference coming from? If both straight and angled deck carriers need catapults and nuclear reactors to take off, that would imply this "huge" cost difference is attributed to solely the deck extension which doesn't seem to add up. Although, it may not be true anymore that you need a nuclear reactor for a jet-capable catapult since there is apparently an alternative to steam catapults now with electric catapults, but those don't sound very cheap either even if no reactor is required.

Another advantage of a canted deck is that aircraft that fail to take off after a missed landing are not run over by the ship.

@RobinBennett Yeah I just saw that mentioned somewhere.

Correct, at the weights and speeds of most carrier based jets they would need several lengths of an aircraft carrier to get airborne.  Catapults became required as the airwings transferred to jets in the 1950s and 1960s.
Aircraft are stored in the hangar below decks, and on the sides.  Anywhere there is free space.  Even during simultaneous launch and recovery.  Look at photos and videos, it can get crowded!
Since we aren't building straight deck and angle deck carriers that are otherwise similar, a fair cost comparison cannot really be made.  (Amphibious ships serving VTOL aircraft lack catapults and arresting gear which would account somewhat for their lower cost.)  Propulsion, radar systems, inflation, and many other factors also account for the increased cost of modern carriers over earlier straight deck ships.  And it is not true that you need a nuclear reactor to generate steam for the catapults.  Steam catapults were around for quite some time before the first nuke boat.

ADDENDUM:   There isn’t enough space in the comments section to refute the multiple inaccuracies in Peter Smith’s response to this question, so I will address them here:
All modern US Navy carriers have 4 catapults, 2 at the bow and 2 at the waist.  (This has been consistent for the last 40-50 years)  The “waist” catapults (cats 3 & 4) are so named because they are amidships, and thus cannot be used during landing operations because they foul the landing area.  The photo in his answer shows the two bow catapults.  The one pictured on the right is NOT a waist catapult, it is cat 1.
Simultaneous launch and recovery is possible however.  Generally the launch starts first while the previous cycle is holding overhead, using all 4 catapults for efficiency.  Once they get to a point where most of the next cycle is airborne and the landing area is clear, they will “wrap” the waist catapults and begin recovering the earlier cycle while they finish launching off the bow.
The only caveat is that longer wingspan aircraft like the Tomcat and E2 will foul the landing area if they are on the left bow catapult (cat 2) with their wings spread.  For this reason they will finish launching them from the right bow catapult (cat 1) if recoveries have begun.  This is not a problem with Hornets, and possibly not an issue on the largest of carriers.
There is almost always some overlap where simultaneous launch and recovery occurs during normal cyclic operations.  And during pilot qual/requal, the deck runs continuously.  You will land, fold your wings, taxi to the bow cat, spread your wings and launch again...  It is a continuous stream of simultaneous launch and recovery operations.
It is also definitely not true that aircraft are not parked anywhere but the bow during recovery.  Any spot outside the landing area foul lines is fair game.  It is a very common sight to see aircraft parked on both sides of the landing area on final approach.  But don’t take my word for it, there are lots of videos and photos on line to verify this…
Finally, the arresting cables are not forward of the “aft lift” you show in your photo.  (Elevator 1 or JBD?)  Again, this photo is of the bow only.  The two waist catapults and the landing area are well aft and left of the perspective this photo was taken from.
BTW, the diagram of the angle deck carrier in the question is not an accurate representation of the current class of US Navy fixed wing CVN Carriers.  Below is a good diagram showing the layout of the 4 catapults in relationship to the landing area.

Trivial note: catapults appeared late in WW2, first used on the very small escort carriers, who needed them even for existing propeller driven aircraft because the decks were too small to launch even Hellcats and Avengers the traditional way.

When talking about catapults and reactors, are you sure you're talking about steam catapults being around for a long time and not the hydraulic catapults which weren't sufficient for jet aircraft?

Yes, I cruised on the USS John F Kennedy which was a conventionally powered ship with steam catapults.  And there were many others...

@MichaelHall Oh, I see. I was under the impression that all the Nimitz carriers were nuclear powered.

You are correct, but the Kennedy was not a Nimitz class Carrier.

The French carrier Foch  was also a non nuclear ship with steam catapults

The diagram shows the conventionally-powered USS Kitty Hawk, CV 63.

Yes, but lacking dimensions if it weren't for the number it could be almost any carrier from the late 1950s to present day.  I realize that there are subtle differences that those who served might appreciate, but there are many similarities, mainly in the 4 catapult configuration.

Catapults 3 and 4 look really close together. How are those normally used? It doesn't look like 4 can be used at all while anything is waiting in 3 so do they set both up before launching both in a row?

@DKNguyen, good observation.  If memory serves me correctly you could taxi an aircraft into position on Cat 3, but if anyone was ready to launch on Cat 4 you would need to keep your wings folded until they were airborne.  They definitely cannot be used at exactly the same time, basically they would take turns.

Modern aircraft that are not VTOL or STOVL cannot achieve combat effectiveness on a straight deck, without a catapult or a ski jump ramp.

An unassisted takeoff from a straight carrier's deck is within the capabilities of some modern naval fighters. But it would severely limit the useful load (fuel and ordnance) that can be carried, and may be impossible in some conditions.
Ski jump takeoff places some restrictions on useful load, which depend on current wind over deck. It also restricts the carrier to operating either high-performance fighters, which can make the most of the ski jump, or helicopters.
Catapults are the highest-performing option, allowing aircraft to use most of their permitted take off weight in most conditions. Additionally, catapults can launch low-powered aircraft such as the E-2 Hawkeye, C-2 Greyhound, enabling the widest selection of aircraft among carriers.

Aircraft deck park storage can be reduced by the operations currently being performed. In general, carriers will operate in such a way that they can both launch and recover aircraft at all times. All rates can be limited by collision avoidance.

The peak sortie rate for USN carriers, over a week-long exercise, has been recorded at about 240 sorties/day, and weekly sustainable rate at about 200 sorties/day. In other words, about 10 aircraft can be landed and recovered per hour. This rate can be exceeded briefly, but, still, only a fraction of the entire air wing can be in the air simultaneously at any given time.
Moving parked aircraft is not fast at all. So carriers stick to simultaneously maintaining both capabilities, although larger carriers may trade some of it for a larger deck park.

Catapults themselves are expensive and maintenance-intensive. They don't require nuclear reactors, but nuclear reactors offer "free steam", which makes things easier. Non-nuclear carrier with catapults usually have or had a steam powerplant with oil-fired boilers. So there's a high cost to fitting a catapult:

More weight at the top deck means more weight elsewhere in the ship.
Modern ships are no longer built with steam powerplants, but with diesels and/or gas turbines. Steam would have to be generated separately, and that's one more maintenance department.
EMALS is meant to be less maintenance-intensive, but it's still heavy and expensive.
More maintenance means more crew, which once again means a larger and more expensive ship.

As a result:

Flat tops without catapults or ski jump are used for the lightest/cheapest carriers for helicopters and VTOL.
Ski jump adds only a little cost and weight, but takes away some area from a deck helicopter park. For carriers primarily meant for fleet air defense (light AtA payloads, moderate range requirements), this is usually a good compromise.
USN carriers, used for force projection, fly large fighters with heavy payloads, often a considerable distance inland, plus a variety of support aircraft. These requirements call for catapults, to launch the heaviest planes, as well as aircraft other than fighters, with low power/weight or thrust/weight ratios.

How do nuclear reactors produce steam for their catapults? Electric heating?

@DKNguyen Nuclear reactors just produce heat, so they work as a fancy kind of steam boilers. It's the steam that is then sent to steam turbines to power the ship - and/or the catapults.

I'm just a bit confused since you kind of implied catapult steam was obtained differently with gas turbines than with nuclear reactors when it sounds identical to me.

Nuclear plants can produce virtually limitless steam, and most of the complexity is not making more than you want, so you just turn the dial a bit when the catapults are in use. Any other type of plant has limited output, meaning you have build it much larger (meaning more maintenance) to power both catapults and propulsion at the same time.

@DKNguyen Catapult steam is obtained differently with gas turbines than with nuclear reactors. Nuclear reactors produce steam and feed it to catapults and steam turbines. Gas turbines don't produce steam, so it requires a separate system. That could be a boiler, for instance.

@Therac Ah, I see what I did. I was mistaking the steam turbine in the nuclear system which is driven and in turn drives the electric generator or propellers, for the gas turbine which is a prime mover and can just turn the electric generator or propellers directly.

Downvoted because you bought into Peter Smith's answer on #2.

Aye... Considering the way voting on Peter Smith's answer seems to be going, you may want to avoid referring to it.

@MichaelHall I was just lazy to address what already got a very long answer... Now that I look at it closer, it does make a lot of claims that just don't match reality.

@Therac, downvote removed.

To answer the questions you asked:
1) It isn’t a question of whether a STOVL aircraft can takeoff on the angled deck of a CATOBAR ship, It’s a question of how much payload the jet can carry doing so.  Short takeoff aircraft like the Harrier or F-35B can only perform short takeoffs aboard ship with limited warlords as compared with jets launched by catapult.
2) This all depends on the class of ship and the layout of the flight deck.  Incidentally CATOBAR type ships are in fact capable of simultaneous launch and recovery, depending on the ship.  You’re also comparing apples to oranges here, as you are using STOVL aircraft versus conventional aircraft requiring arresting gear to stop.  STOVL aircraft return and land vertically and, technically, require nothing more than a helipad to do so.
During World War II, Essex class aircraft carriers did allow for simultaneous launch and recovery. This was a risk here as aircraft landing were basically on a one-way approach without the option of a go around. If the aircraft failed to snag a wire it would take a barricade erected before it could make contact with aircraft parked on the bow. Past World War II and going into the jet age, this was not possible as new jet aircraft or larger heavier and much faster and required much greater distances to stop in and arrested landing. The angle deck facilitated this well and also provided for the option of a go around should a pilot need it, either for a bad approach or bolter.
In regards to how quickly a carrier with STOVL type aircraft can lodging recover versus conventional aircraft, when a CATOBAR  carrier is in full launch mode, they can shoot an aircraft every 45 seconds - From each catapult.  On the Nimitz class aircraft carrier that’s gonna be an airplane every 11 seconds! Clearly that is not possible with a single launch of a sort field aircraft from a single takeoff area.  And with a conventional takeoff aircraft, you can launch more aircraft with greater range and greater war loads, as opposed to a smaller carrier requiring the STOVL aircraft.
3) The inclusion of an angle deck is not necessarily indicative of the cost of the ship. Lots of aircraft carriers had angle decks in the past and were nowhere near the cost of a modern Nimitz or Ford class ships. The cost is going to be determined by the size of the ship, the equipment on board, etc.

s/warlords/warloads (I hope)

@ChrisH Nothing devastates the enemy quite like dropping a bunch of warlords into their territory to wreak political havoc.

Trying to do simultaneous launch and recovery on a canted deck is impossible in normal circumstances as the waist catapult and bow catapult are inside the wingtip safety line.
You can also see the catapult wingtip safety lines in the picture incidentally.
I have annotated the picture:

The aircraft with red circles are in the position they would have when loaded onto the catapult and as you can see, they violate the landing area.
Note that the waist cat (the further right of the two) has a much lower angle relative to the centreline than the landing area angle; this is to minimise the angular offset for the aircraft when launched (the carrier will be headed into the wind).
During launch, all aircraft are kept behind the area of the catapults (immediately behind them are jet blast deflectors to prevent the jet blast going all the way down the deck).

During recovery (not landing - an aircraft is actually flown onto the deck well above stall speed to facilitate a go-around often known as a bolter) when an aircraft has been recovered they are moved to the bow area away from the angle (in this situation it is known as an aircraft park); once the angle is properly clear, the next aircraft can be recovered.
No aircraft are usually parked anywhere except the bow area during recovery just in case things go very badly wrong.
The ability to park the recovered aircraft away from the direction of travel of other aircraft being recovered is a major advantage of a canted deck.
The arrestor wires (usually 4) are just forward of the aft lift you can see in the picture.
The usual mode of operation is a launch / recovery cycle. Launch a group of aircraft and then recover the previously launched group. Aircraft not involved in the launch cycle are kept in the hangar(s) or a safe area of the deck (such as the starboard lift in the picture).

So the whole simultaneous takeoff and recovery thing for canted decks is nonsense?

@DKNguyen; I would say yes. I worked on a canted deck (and was on the deck during launch and recovery) for years and simultaneous launch and recovery was never done. For it to be possible, the catapults would need to be well clear of the angle landing area and besides, where would the recovered aircraft be parked?

Your last image shows a second bow catapult which would be usable during landing ops.

@Peter Smith - Downvoted, see the addendum in my answer.  I don't believe that you worked on the flight deck of a modern carrier or you would know many of the things you are claiming are false.  Even a little internet research would refute your points.


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How moral are military aviation patents
I was reading about F-35's version that can take of vertically and it's mentioned that they are using a patented technology by Rolls-Royce called Fanlift and Liftsystem which brings me the questions:
Do other countries have to be partnered with Rolls-Royce to develop such technology (exact one)?
What if Rolls-Royce doesn't want to partner with them?
Isn't this a way of saying: "Here is a way to kill you but you can not kill us back?"
I do not have deep knowledge of patents and how they operate, would be glad to be explained.

Since these patents are only effect on the friendly, not the enemy, I would consider it quite immoral, e.g. US would ask UK, "why are you OK when Russia copied your ideas but not me?" I mean, when two countries are at war, should they sue each other on patent infringement first or on property damage or murder?

"how moral" calls for  an opinion based answer

Patents are designed to make it worth investing in large R&D projects by granting exclusive rights for a few years. If you knew your design would be copied and you wouldn't make any money from it, it wouldn't be worth developing. They're limited to around 20 years so everyone gets to share it eventually, and the company has an incentive to develop something even better.

@RobinBennett 20 years? But how is it in favor of relatively underdeveloped country they are not the one making big money returns from R&D  and they also can not copy the product.

The theory is that a shorter period would prevent companies developing big new projects, because they couldn't make a profit before it was copied, so no one would benefit. The F-35 project started in 1992, so some of their patients will have already expired.

For questions on morality there is Philosophy.SE, for patent law there is Law.SE

Downvoted because unless you explain your personal ideas of morality, it's unanswerable, and if you do, it becomes a question for philosophy, not aviation.  Personally, I rather like the idea of being able to kill my enemies without them being able to kill me back, but that's just me :-)

@jamesqf I see, but it stays here for future reference and a lesson for me to formulate a better question. For your point it's reasonable to prevent enemy to fight back but interesting thing is the "enemy" in this case also agrees on the terms.

A few misconceptions:

All parties want war to be as unfair as possible, i.e. an easy win. Technological superiority is a big part of that. There's nothing 'moral' about war, and there are definitely no gentlemen's agreements to make it a fair fight. Some people argue that a fair fight leads to a longer war with more casualties, so arguably, it's immoral to have a fair fight.
Patents are not "it's impossible to copy X". It means you can sue the person who copies X. To successfully sue someone, you need a functioning legal system, and to sue across borders, you need countries to acknowledge the validity of each others courts. If a country is at war with another, none of that holds.

Patents are a way to protect the economic interests of a company. You cannot win a war with patents.

Completely agree with first point, However, for the second point :  you need military equipments before the war not during the war. In addition, war is not the only point because international politics also affected by direct proportion of their military power against rivals. Not to mention China already stoke TBs of data about F35 project but still couldn't even came close to produce an aircraft in the level of F35

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


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Adding IFR to an Experimental
I am considering buying an Experimental-Amateur Built plane. It was originally equipped and approved for VFR only.
The second owner completely redid the avionics, and it’s now a solid IFR platform and fully compliant with 91.205(d) as far as I can tell, but they never got the Operating Limitations updated to allow IFR.
What all is involved in correcting that oversight?

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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FMC and MCDU not talking
I have a test bed in which the FMC and MCDU are hooked up to one another.
FMC menu was populated on MCDU and was able to be navigated.
After making some changes to the FMC GPS #2 lines, the FMC started acting up and would then fail.
Since failure, the FMC menu would no longer display on the MCDU even after the fail was cleared.
Just wondering what is it that I’m missing.
No wiring from FMC to MCDU was touched and only GPS & IRS busses 1&2 were ever replaced.
We can tap into the FMC and see that it is sending some data to the MCDU but the FMC menu still fails to populate.

What PN are you talking about? Are you using OEM hardware? So many questions....

Welcome to Aviation Since not everyone here is an expert, can you add more details to your question?

Assuming the MCDU is ARINC 739A compliant (almost all are) the logic behind the menus is entirely within the FMS. The MCDU is just a dumb terminal.
When you press a button on the MCDU it just sends a message to the FMS that that specific button was pressed. The data displayed on the MCDU is just ASCII characters sent from the FMS within a command to write the text on the specific display location (line/column).
Your best option is to swap in a known good MCDU and see if anything changes.
I expect the failure is most likely within the FMS.


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Why are engines with carburetors hard to start in cold weather?
Why are engines with carburetors hard to start in cold weather?
And why is there a different procedure for hot start scenarios, after you've just shut down the engine and want to power up again?

They are all harder to start in the cold, fuel injected engines included, and need an over-rich mixture for starting.  The rich mixture is required because a lean one is harder for a spark to light off if the fuel/air charge is cold.
Now, it's still cold outside after the engine warms up, so the air charge is still cold, initially, but on a warm engine it gets heated as it extracts heat from the intake passage, valve and cylinder head on its way into the combustion chamber (and on Lycomings, the carburetor, which is bolted directly to the oil sump).
Carbureted aircraft engines use primer systems instead of chokes, as mentioned in AEhere's answer, because it's undesirable to have that sort of obstruction device in the intake passage. The primer injects raw fuel at the intake port using a syringe type hand pump, most of which settles on the intake passage walls and runs down the tubes a bit, and sits there slowly evaporating, and when the engine cranks, the vapours add to the fuel normally drawn at the carburetor.  It does this for a period of time after the engine starts depending on how much prime you used.
Fuel injected aircraft engines are primed the same way, but since there are injectors already there at the intake port they don't require a separate primer system.  You just turn on the fuel pump with the mixture rich for x seconds and it injects raw fuel just like a primer system.
Carbureted aircraft engines also use a slightly richer than necessary setting in the idle circuit to help them run better when cold.  That's why you get a little rpm rise when pulling idle cutoff.
You can have too little primer fuel when starting, or too much, and it varies widely depending on the engine, its temperature, and the air temperature, so you have to learn how much is enough on each engine type.  A typical protocol is:

On a cold engine in warm weather, you might use 4 strokes of prime.
On a cold engine in cold weather, you might use 6 to 8 strokes of prime.
On a warm engine in cold weather, you might use 1 or 2 strokes of prime.
On a warm engine in warm weather, or a hot engine you just shut down, you usually don't need any prime, but may use a little half-shot of prime, or, if the carb has an accelerator pump, a short stroke or two of throttle applied while cranking (to avoid fuel running down into the air box since throttle pumping sprays extra fuel from the accelerator pump right at the carb, and if the engine backfires with fuel in the airbox you can have an intake fire).

Different engine models have different starting quirks, and different primers have varying fuel volumes per stroke.  It's something you learn on that engine type, along with whatever other unique characteristics of a particular aircraft you have to be aware of.

Also fuel injected engines (at least automotive ones - I've never dealt with an aviation one) have electronic systems that supply exactly the right amount of fuel for a given temperature, rather than just a rule of thumb X strokes of prime.

Yes aircraft engines of the traditional type are basically like 1930s tractor engines, complete with magneto ignition, except for being air cooled and much lighter.  However, the "crudeness" of these engines is a plus when your life depends on them, and the theoretical loss of efficiency of not having the latest features is just not that big a deal.   For example, to use an EFI system on an airplane using solid state electronics you have to use an architecture with zero single points of failure, which means two of everything all the way up to the power source.  Then try to certify it.

Well, carburetors have points of failure, too.  As I learned while doing an annual on our Cherokee: looked at the carb, and discovered the float bowl was loose enough to leave about a 1/8 inch gap between it and the carb body.

Well yes but I left out the other part:  where you do have single points of failure, there are simple mechanical components where degradation can be detected most of the time while it is still more or less functional, or giving strong hints of something amiss before it finally lets go.  The  point about electronics is the sudden failure mode without any warning that necessitates much more elaborate redundancy.

Carburetors don't work as well in cold conditions because they themselves tend to cool the air as it flows through the Venturi tube, compounding the issue of cold intake air and cold fuel.
From Wikipedia:

When the engine is cold, fuel vaporizes less readily and tends to condense on the walls of the intake manifold, starving the cylinders of fuel and making the engine difficult to start; thus, a richer mixture (more fuel to air) is required to start and run the engine until it warms up. A richer mixture is also easier to ignite.
To provide the extra fuel, a choke is typically used; this is a device that restricts the flow of air at the entrance to the carburetor, before the venturi. With this restriction in place, extra vacuum is developed in the carburetor barrel, which pulls extra fuel through the main metering system to supplement the fuel being pulled from the idle and off-idle circuits. This provides the rich mixture required to sustain operation at low engine temperatures.

To put it in simple terms, carburetors create a combustible fuel air mixture by letting fuel evaporate into a stream of air in more or less controlled conditions. To do this, they reduce the pressure of the air by forcing it through a Venturi tube; this facilitates fuel evaporation.
An undesirable side effect of the process to reduce the air stream pressure is a drop in temperature. A lower temperature makes it harder to vaporize the fuel, and if the intake air and fuel are already colder than usual, the resulting mixture might be too lean to burn.
This is countered via special cold start devices such as chokes, manual mixture control and heaters. Of course if the engine is already hot, having been shut down recently, it might be able to restart without such contrivances. Keep in mind, however, that the carburetors will usually cool much faster than the engine block, being smaller often exposed to more airflow, and all it takes is for them to cool down to impede a restart.

Hot starts are sometimes difficult on fuel injected engines because the engine heat will boil the fuel in the fuel lines, creating a vapor lock.  Fuel pumps are designed to pump liquid fuel, not fuel vapor. The same is true for carburetor engines, although usually not as severe.
Look at your POH hot start procedure.  Usually this involves running the fuel pump to move liquid fuel into the lines, flushing out the fuel vapor, and in most cases flooding the engine as well.  Then the flooded start procedure must be used.


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What will be the immediate action by the pilot and ATC if any plane blocks the runway while landing?
Suppose, if the Airport has only one runway and one plane is trying to take off at the end of the runway and other plane trying to land from the other end of the runway.
Due to any reason if the pilot decides to abort the take off.
In that situation that plane is blocking the runway and it is in the way where the other plane is trying to land at the same time.
What action will be taken by the pilot who is landing the plane and what action will be taken by ATC?
Is there any chance of collision?

I don't think this is a duplicate. The linked question is asking what happens if a runway is closed well in advance of aircraft that want to land; this question is asking what happens if an aircraft unexpectedly blocks the runway while another plane is trying to land.

I read the question as one plane land and one plane takeoff from opposite end of the runway. This would not happen at controlled airport.

The scenario is unlikely because starting and landing, at least on controlled airports, happen in the same direction; even on uncontrolled airports they normally would with any wind that's not exactly perpendicular to the runway. (That said, an aborted start would still block the runway even if being in the same direction.) Oh, @vasin made that point already, partly.

ATC will tell the landing plane to go-around. The pilot will then execute the go-around by flying the missed approach procedure as published in the airport charts.
Go-arounds happen daily and are pretty much a routine action.
In any case, if the landing pilot feels that the runway is not safe for landing, he can decide to go-around by himself without ATC order (if the controller missed the issue or if the airport is uncontrolled for example).

For reference, the missed approach procedure can be as simple as:

Stopping descent
Climbing back to a published altitude
Flying a published pattern
Trying a second approach

it can be done if there is enough time for performing this operation. what if landing plane is just about to touch the ground and it can not abort the landing?

This is not supposed to happen. If the departing plane has not cleared the runway soon enough, ATC will issue the go-around order. They don't wait for the last second. The landing plane will have plenty of time to comply.

@Snow I edited my answer to reflect your comment. Thanks!

@Deepak-MSFT "what if landing plane is just about to touch the ground and it can not abort the landing" - there is no point where the landing cannot be aborted, up to and including when wheels have touched down. There comes a point where you have reduced speed so far as to not have enough runway left to take off again, but in the situation you supply, this is not possible.

I suggest you clarify that "go-arounds" happen daily and are routine, but not for reasons of runway incursions, which are quite rare and extremely serious.

@abelenky done ;)

Could you also clarify that missed approach procedures are published but go-around procedures are not. What usually happens at busy airports is that the tower will say ”fly runway heading and contact approach.” At smaller airports they will just have you enter a left or right traffic pattern.

@JScarry thanks for the suggestion. I edited my answer to reflect that.

Missed approach procedure only apply to IFR aircraft. VFR aircraft will usually be told to make left/right traffic after a go-around. Some IFR aircraft, particularly light ones, may choose to do that as well if in VMC.

Out of curiosity, do you remember that incident with an Air Canada plane landing despite being told to go around and a plane blocking the runway at San Francisco airport?

It may also be worth mentioning that the instruction "cleared to land" is not issued until the departing aircraft is clear of the runway. In such an example of an aircraft aborting its takeoff, the approaching aircraft may well have reached their decision altitude and failed to hear the instruction "cleared to land" and will have already aborted their landing attempt, and reported "going missed" to the controller, before the controller has issued the instruction "go around".

@GavinCoates this is not true. ATC may clear you to land while the runway is still occupied. They will then cancel the clearance and ask you to go around if needed.

@QuentinH are you sure? I used to listen to ATC at Edinburgh back before they had full length taxiways, so they regularly had go-arounds due to aircraft missing the exit. Aircraft on approach would be told to "expect late landing clearance", then would only be issued "cleared to land" instructions once the runway was clear.

@GavinCoates I got cleared for landing while a plane didn't even started rolling for take off on the same runway no longer than last week. The controller just added that this plane was about to go. But I was VFR in Europe. Anyway, I listen to loads of ATC every week and I'm pretty sure I heard that happen more than once.

@GavinCoates see this answer: https://aviation.stackexchange.com/a/1465/10076

one plane is trying to take off at the end of the runway and other plane trying to land from the other end of the runway

That would never happen. Planes are under ATC control from the moment they start their engines until the moment thay shut down their engines at the destination. (This is a simplification, but for the context of this question it makes sense).
ATC decides basically everything a flight does: which way it taxies, where and when it takes off, which way it flies, how high, how fast, when and which runway to approach and when to land. ATC will always ensure that there is enough separation between flights so that there is no risk of collision. That is literally the main reason ATC exists.
Generally speaking, only one aircraft is allowed on any one runway at a given time. While a plane is taking off from a runway, another plane cannot be cleared to land on that same runway. The aircraft approaching will not be cleared to land until the departing plane is in the air. If the departing plane decides to abort takeoff, ATC would simply instruct the landing plane to cancel the approach, and then direct it around for another try.

That would never happen INTENTIONALLY. There are plenty of examples of situations where due to some reason or another 2 planes ended up on the runway at the same time, although this usually is caused by extreme fog conditions, in which case the pilot probably wouldn't be able to see the obstruction.

@Nzall Sure. As stated, my answer is a simplification.

It may never happen in theory,but does happen in practice, I witnessed myself once.A BA flight to Nassau stopped its landing (it was night, I am not sure how close we were, but clearly the ground was visible) and regained altitude. First announcement: we had to cancel the landing for security reason, more details later. Second announcement: since it is dark, there was a plane on airport ground whose location is not known precisely so to avoid hitting it on the runway if it is there we decided to cancel the landing and go around. Second landing was fine. Of course, it is only what we were told.

Also the airtraffic is monitored, but not really controlled by ATC in the sense that the pilot flying has the absolute authority, where to fly. ATC simply tries to manage the requests and proposes flight paths that conform to established routes.
Still the rest of your answer applies. +1

@PatrickMevzek Uhm yes. That's exactly what I wrote in my answer. If the runway  is blocked, ATC will instruct the pilot to cancel the approach. Exactly as you experienced.

@Spacy If the plane catches on fire, sure, the pilot has the final say. But 99% of the time, ATC decides which way to fly.

The air traffic controller will instruct the landing aircraft to perform a go-around.
It is part of the air traffic controller's job to ensure there is always enough spacing between a departing aircraft and a landing aircraft to accomodate such a situtation.
A situation similar to what you describe is in this youtube video:

Note that in this case the clearance to land was given before the departing aircraft left the runway. This is quite normal in the USA, but not allowed in many countries.
Usually the clearance to land is only given after the departing aircraft (or previously landing aircraft) has left the runway. The landing aircraft is cleared for the approach to the runway, but not for the landing itself, until the runway is clear. Should the departing aircraft be stuck on the runway, and the communication to  the approaching aircraft fails as well, the situation is still safe since the approaching aircraft is not cleared to land and will therefore have to go around.

Is 'clearance to land is only given after the departing aircraft has left the runway' a European rule? I fly in the US as and land at Class D and Class C airports. I am often given a clearance to land as number 3 or 4. e.g I am told to follow a Cessna on 4 mile final. I report them in sight, then I am told, “Cleared to land number three.” I also get cleared to land and they inform me that several aircraft will be departing in front of me.

@JScarry not so much European, many countries operate this way. US is the best known exception, but there may be others.

ICAO rules prohibit clearing more than one aircraft to use a runway at a time. The FAA, however, allows it in many cases under their "anticipated separation" rule.

@StephenS Indeed, ICAO describes it almost to that effect: ICAO Doc 4444 (PANS-ATM) section 7.10.2 (Clearance to land) states: An aircraft may be cleared to land when there is reasonable assurance that the separation in 7.10.1, or prescribed in accordance with 7.11 will exist when the aircraft crosses the runway threshold, provided that a clearance to land shall not be issued until a preceding landing aircraft has crossed the runway threshold.

@DeltaLima I've been "number 8, cleared to land" while in the pattern. There is no way you can do that under ICAO rules.

@StephenS no, that's not possible under pure ICAO rules. FAA deviates from the ICAO SARPS there.

This doesn't just happen, it is a situation that develops.  That developing situation will be watched closely by ATC, who will communicate with the approaching aircraft.

"Its speed was mini"
Note how the approaching aircraft can hear ATC trying to talk the A318 off the runway.  Also notice how they call "go-around" (abort) immediately after "Minimums" is called out.  Minimums is the normal decision point where you abort the landing if the aircraft isn't positioned, configured and stabilized, the runway isn't seen, runway isn't clear etc.
Double trouble: Route interference
There's actually a worse situation than what you propose.  You have the aircraft NOT taking off, and we've shown that's straightforward.  What if it does successfully take off?
Now we have a route conflict and a collision risk, not just on the ground, but in the air.    Watch this.

Green (Ukraine) was lined up for takeoff, but wasn't fast enough to get out of purple's way.  *At this point, it is a foregone conclusion that purple (KLM) MUST go around.
But there's a problem.  On a standard go-around, you fly runway heading - climbing over the runway and continuing that "line".   That means for Purple to go around, Green must not be in that air!  That's why Green was ordered to stop and hold on the ground even though he'd already started his takeoff roll.
Unfortunately Green had some "radio trouble", and continued the takeoff anyway.  He would be in exactly the on-runway-heading space that Purple needed to "go around" in.
So ATC made an urgent radio call to Purple telling him to immediately turn to another heading.  "Go around, immediate right turn heading 010".  If that radio contact had failed, Green and Purple would be flying in the same airspace, and relying on visual observation to miss each other.
It was presumed that Green was unreachable because of his "radio trouble".  Just as likely, Green realized that if he aborted takeoff here, he'd have to pull off to a ramp, work a hot-brakes procedure, and then get back in the queue to takeoff at this busy airport, with an hour or even more delay, maybe with disruption to the schedule for the rest of the day. So he decided to have "radio trouble" and let ATC clean up the mess.  That's no way to make friends in the tower!

It can happen at uncontrolled (no ATC tower) as well (which are the vast majority of airports in the US). Initial reaction is to apply power to help with a climb and then start "cleaning up" the airframe - retracting landing gear (if so equipped), start flaps retraction (and slats, etc) and continue climbing. At some point, make an announcement on CTAF ("Marlboro traffic, Nxxxxx is going around") or the same to the tower ("Worcestor tower, Nxxxxx is on the miss" if shooting an instrument approach, or "Worcestor tower, Nxxxxx is going around" if VFR, tower will likely provide directions.
The situation can happen at either end of the runway.


text:
How did pilots maintain the Vomit Comet's parabolic trajectory?
How did the Vomit Comet maintain its free-fall trajectory?  Careful trimming?  Custom autopilot software?  Or just good stick and rudder technique?
Wikipedia, citing references but without substantiation, suggests manual control of at least the throttle. To use an automotive analogy, a trained pilot could correct for which direction the fuzzy dice are hanging from the rear view mirror, by playing the throttle and elevator and spoilers.  But even a legend like Bob Hoover might lose precision doing that dozens of times in a row.

I'm not sure about the "Vomit Comet", but the "Zero-G" A310 has a "very simple" device that allows one pilot to control the aircraft vertically, and the other pilot to control it horizontally. This indicates that each parabola is manually flown using a G-meter.

And sheer inertia suffices to control it along the direction of flight, I guess, because that isn't mentioned.

I'd think that the horizontal control (i.e. roll) would be pretty straightforward; keeping the pitch control nice & smooth would be the challenge for whoever has the yoke, and precise speed control so that the free-floating folks in the back aren't sailing toward a fore or aft bulkhead as the jet gains or loses speed.  I'll be interested to see an authoritative answer to this question!

You can do the same thing in any light plane. It's just that the duration of your 0G ride is only about 3-5 seconds, and the engine will quit during the zero G part unless you have fuel injection.  Dive, pull up, push to make the pencil float in front of you until you're back diving at the ground.  Push a tiny bit too hard, and all the crud on the floor ends up on the roof.  Done that.

Organic Marble's answer says that thrust is modulated, manually.  So the A310 would need that too, perhaps automatically.

@John K: You can do it in sailplanes, too, so you don't have to worry about the engine quitting :-)

The NASA Vomit Comet was flown manually.
From The dynamics of parabolic flight: flight characteristics and passenger percepts

The control inputs required by the pilots of a parabolic flight aircraft are relatively simple, although precision is required to make the 0 g phase as close to freefall as possible, and care is required not to exceed the load limits of the aircraft which at times flies near its maximum rated speed. The pilots modulate lift L with the elevators and wings, which indirectly changes attitude θ, and thrust T with the engines (Figure 5).

....The pitch angle of the aircraft is not directly controlled by the pilots, but is a secondary result of other control inputs. During level flight the wings produce an upward lift, while the tail-mounted elevators produce a small downward component of lift in order to maintain a desired pitch angle. When flight conditions change, such as when the pilots deflect the elevators down during freefall, the relative forces from these two surfaces change. Since their moment arms are different, this causes a shift in the center of lift so that it no longer coincides with the aircraft center of gravity, resulting in a torque that causes a pitch rotation of the aircraft.

..At approximately 225 KT IAS (360 KT TAS, 185 m/s, Mach 0.61), when the aircraft is pitched nose-up 45°, the pilots commence the 0 g parabola. They push forward on the control yoke ("push over") to lower the angle of attack of the wings, which reduces wing lift, and simultaneously reduce power to a level just sufficient to overcome drag.

...After 25 seconds, at the end of the parabola, when the nose is pitched down 45° and airspeed is close to 350 KT IAS, the pilots pull up (pull back on the control yoke) and increase thrust to change the aircraft’s downward velocity into upward velocity, and restart the cycle.

"The pitch angle of the aircraft is not directly controlled by the pilots, but is a secondary result of other control inputs."  Other control inputs like pushing and pulling the yoke?!  From a pilot's perspective you cannot control pitch any more directly than that...

I think what that that statement means is you are using elevator differently - to stay on the ballistic path, not to control attitude in the normal sense ("pitch angle" in the excerpt), with attitude changing continuously while flying the arc.  In other words, when flying the arc your pitch control input is directly tied to maintaining zero G, independent of attitude, while in the arc.

Happy to see a familiar face from the Space Exploration site!

Note the orientation of the nose WRT gravity vector changes during the maneuver.  Were it not for air drag, one could simply chop power and go "ballistic".

@MichaelHall even I agree that that statement sounds weird and contradictory.

Whatever the author meant to say it was, at best, an odd choice of words.  Pitch is defined as rotation about the lateral axis.  You control pitch with fore and aft movement of the control column.  It doesn’t matter whether your target is attitude, airspeed, AOA, or Gs, that is your primary control for pitch.  What “other control inputs” are there?

Note that the image shows generic steady descent, not 0G flight. In 0G flight the lift must be zero, and the thrust must exactly balance parasite drag only!

@Jan Hudec at the top of the arc thrust is perpendicular to vertical acceleration.  Net zero G must be created by turning an arc, just like in orbit.  A given velocity and rate of "turn" must create the "-1 G" to offset gravity.  The maneuver is also possible (and maybe a little easier) by rolling 90 degrees and using rudder.  The wing will no longer drag vertical acceleration.

@RobertDiGiovanni, lift is, by definition, the aerodynamic force perpendicular to the flight path, and that must be zero. Drag is, again by definition, the aerodynamic force parallel to the flight path, and that must be balanced by thrust. The gravity is then the only force left that curves the flight path. There is nothing to offset it so the plane can be in free fall.

Zero G parabolic flights can be flown "hand flown" manually, as illustrated here:

Parabolic maneuvres piloting technique
Unlike commercial flights, the Airbus A310 Zero G is simultaneously piloted by three members of the flying crew during the parabolic manuevres.
One pilot controls the pitching (nose-up and nose-down angle). A second pilot controls the roll movement (to keep the wings horizontal). A third pilot, sitting behind them, controls the engine speed (he or she also monitors the flight parameters: warnings, temperatures and pressure).
Together, all three pilots maintain a near-zero acceleration level in the three axes to guarantee zero-gravity precision ± 0.02 g
Unlike in a standard aircraft, the pitching and roll control commands are dissociated. The two control column functions are dissociated by the use of an additional control column on one side and two small cables hung from the conventional control column.


text:
Advantages of an inverted sesquiplane?
A biplane whose lower wing is significantly shorter in span than the upper is sometimes called a sesquiplane, from sesqui "one and a half."  One whose upper wing is shorter (even slightly, because it's so rare) is called an inverted sesquiplane.
Examples include:

the 1924 Fiat CR.1 fighter
and its immediate successor the CR.20

the 1927-ish Caproni CA.73 airliner

the 1929 Caproni Ca.90 bomber.

Why would a designer of that era have chosen such a layout, instead of making the longer wing the upper one?
For a century now this layout has fallen into disuse, despite modern homebuilt biplanes, even despite Burt Rutan.
All that I can think of is that the enormous Capronis might have needed extra ground effect from the lower wing.

I would think materials of the time might be one of the major reasons, and for fighters the shorter wingers are apparently good for dog-fights.

@MrR I've narrowed down the question to: why is the bigger wing the lower one, not the upper one.

Brilliant, @jkztd.  Big wing on top would have made for an, um, exciting release!

This is a really good question. I have to admit that I am baffled by the few designs which use the inverted sesquiplane layout.
Possible advantages I can come up with:

You can use the same wing design and place the lower wing halves left and right of the fuselage and join the upper wings directly above the fuselage. Now the lower span will be wider by the width of the fuselage, but you only need one set of jigs.
The upper wing will not only have less span, but also less chord (now you need two sets of jigs, bummer!). With less chord it also is less in the way of the pilot's field of view, especially in turns. This is only valid for small planes with the pilot seated close to the center of gravity, but will not apply to the large Caproni designs.
If you put ailerons only on the lower wing, where they have a larger lever arm, the control cables can be run directly between the stick and the  bell crank for the aileron, so there is less play in the roll axis controls.

But the disadvantages are also obvious:

Less bank angle is permissible before you have wing tip contact during landing.
With more lower wing chord, less ground view is left for the pilot, especially when seated close to the center of gravity.
Especially important for the adherents of the pendulum fallacy: The sesquiplane is believed to be more stable in roll.

Why does the the upper wing's chord shorten?

The deficit in the upper wing's span is quite a bit more than the fuselage width, in the 3-views I found.  But even so, that could have meant fewer jigs.

Lower-wing ailerons are plausible especially for the CA.73, where they extend past the wingtips.  Mr. C. may have thought that improved roll control would prevent tip strikes better than a shorter lower wing.

@CamilleGoudeseune Why shorter chord on the smaller wing? Because it is meant to provide less lift. That has often been done on regular sesquiplanes, so why not on inverted ones? I do not refer to any of your examples in particular, but the concept in general.

Pendulum "fallacy" again?  Put a few tons of weight (possibly taken from a sailboat keel https://improvesailing.com/sailboat/keel/weight ) on the bottom end of a long, rigid, fixed pole projecting 50' down below the bottom of the airplane and see if the shift in CG location, coupled with the sideslip dynamics inherent in any uncommanded turn, don't produce a significant change in the hands-off flying characteristics of the aircraft.  If still unconvinced, re-position the pole to project upwards above the aircraft rather than downward below--

One might be especially fascinated by the airliner design, as the sesquiplane plane structural box was strong, tried and true, and allowed a good place to mount the (more efficient) double propeller.
The Caproni CA.73 airliner could lift 2 tons and fly at around 100 knots, well within the aerodynamic speed limitations of biplane designs, with 2 500 Horsepower engines.
The "inverted" sesquiplane very thoughtfully makes use of ground effect to assist in short/muddy field take offs.
Though many may scoff at biplane designs with more modern materials available, one can't help to notice that thinner wings are better in the high subsonic realm that many airliners operate in.
A proposed airliner design bears an uncanny resemblance to the (non-inverted) sesquiplane, which could allow for higher aspect wings with adequate strength.

How do thinner wings, either literally, or greater aspect ratio, relate to the question?

@CamilleGoudeseune monoplanes with thicker wings are stronger, but the sesquiplane design may make a comeback for high subsonic airliners.  Thick wings do extremely well until Mach effects add to drag.

Gotcha. The article proposing a strutted airliner makes sense. But how does that relate to why someone chose (and might again choose a century later) the lower wing rather than the upper to have greater span?

@CamilleGoudeseune I believe you had it right by suggesting ground effect, as many airfields at that time simply were not made to handle larger aircraft.  Using ground effect this way was not a bad idea.

So true.  Back then the runways for heavier airplanes were usually water.


text:
Deicing Rod for Propellers
Similar to a card hitting the spokes of a bicycle, the card is soft enough to knock the dust off the spokes with no damage. What material would be best to impede the propellers to chip off the ice. Assume the flexible rod is machine held. What heavier duty impeller could be used for this? What about the same idea for a helicopter rotor?
I apologize for the multiple questions but they could not stand alone on their own. If it an issue let me know.

What does this solve that deicing boots or heat plates do not?

I would suggest a machine gun firing through the propeller, with no synchronization mechanism.  Firing blanks of course.  Or... not.

@quietflyer using concussion to clear the ice. hmmmm.

@quietflyer excellent a machine gun could be timed so precisely to chip of the ice. Maybe salt rock.

A rod soft enough to not be quickly destroyed by the propeller (or to damage the propeller) would likely be too soft to apply impacts forceful enough to shatter ice along the full length of the blades.
A "baseball card" big enough to handle the full length of the blades, and also soft enough, would likely be blown aft forcefully enough to not touch the prop at all.
Frame challenge:  so-called deicing boots accomplish the same, with no risk of damage and with proven reliability, by electrically heating the blades to melt the ice.

Maybe a propeller can be made with leading edge meets the rod where the contact is just with the ice and not the propeller or rotor?

How could that work when ice is on a blade's leading edge?

@Justintimeforfun Would make an interesting challenge for constant speed propellers (variable pitch). Either way I think you are trying to solve a problem that has simple, effective solutions already.


text:
What is this helicopter type at a U.S. military base?
This helicopter is on a US military base, shown by Google Maps. I don't recognize the glass windows at the front top.

Google uses algorithms to compress their image data. They will identify the object and represent it with a symbol, and translate the symbol to an image when presented to the user. This is why all cars in parking lots looks like the same car, because they are all generalized into a generic "car" symbol. Same with helicopters. You can sort of see this helicopter is pasted from a different picture. As a general rule, don't use google earth as evidence that certain aircraft or ground vehicle has been somewhere sometime.

@user3528438 No, it doesn't. Google Earth uses actual photos. It does try to recognize objects so it can extrapolate a 3D perspective, which is what is causing the weird border around the helicopter, but that is an actual photo of an actual helicopter.

@HiddenWindshield It sure is A helicopter, but not necessarily THE helicopter.

@user3528438 Again, no. That is THE helicopter (well, actually a photo of the helicopter) that was there when the picture was taken.

I just zoomed into a parking lot in Google Earth, and every car is a different color and shape like you would expect, some with sunroofs with truck beds; they don't all look the same at all. With 3D mode turned on, the shape is distorted a bit (especially in the case of a car parked under a tree), but turning it off just produces photography. I'm compression is used, but not to the point of making everything look identical at all.

In addition to Peter Kämpf's comprehensive answer identifying the helicopter as part of the Mi-17 family, this aircraft is likely to be a Mi-171E, clandestinely operated by the United States government, specifically it is 15-5207. With respect to 15-5207, the pictured aircraft

is a similar colour to 15-5207
has a similar box in front of its engine intakes (possibly for infra-red reduction)
has the same black triangle design around its exhaust
and has a similar proliferation of aerials on its tail boom.

Mi-171E 15-5207 in Springerville AZ, 2016 (source)
15-5207 was photographed at Felker Army Airfield, Virginia USA in December 2017; the orignal picture from Google maps is also Felker (note the provided link does may not show the helicopter depending on where you are). Felker is part of Joint Base Langley–Eustis. This aircraft has been noted at -

Burbank, California 2016
Yuma 2016
Springerville, Arizona 2016
and in 2018 at Opa Locka, Florida.

Understandably, the American military and secret service use of Mi-171E is not widely publicised, although it's known that the CIA has used the Mi-17 in a number of theatres. This particular aircraft carries no identifying markings; it may be connected with the US Army's purchase of 30 Mi-17s in 2013.
The only comment I can find with regard to this particular aircraft is from the Dutch aviation Scramble magazine on social media -

There are rumors that the US Department of Defense are using Russian
build aircraft for Special Forces Operations in areas abroad where no
western type aircraft operate. Evidence of this is very hard to find.
...
It is known that the US Air Force has the 6th Special Operations
Squadron (SOS),based at Hurlburt Field (FL), which is specialized in
Foreign Internal Defense (FID) operations. The primary role of the 6th
SOS is to assess, train, advise and assist foreign aviation forces in
the use of their aircraft, but the squadron also carries out intra
theater support of special operations forces, flying clandestine
night-vision insertion and extraction, air land and air drop resupply
mission with the capability of operating from unimproved runways.

Mi-171E operated by the US Government (source)

The CIA headquarters is in northern Virginia, the Joint Base Langley-Eustis is in southern Virginia.

Got it, will amend.

Looks awfully like a Mil-17, more specifically a Mil-171. This is a development of the Mil-8 and known as Mil-8M in Russia but called Mil-17 when exported.

Five rotor blades.
Multi-segmented canopy windows.
Raised tail rotor on the left side.
Small horizontal tail on the rear tailboom.

Below is a different view of the same spot from Google. Count the number of front windows:

and compare it with this one:

Czech Mil-171 (picture source) which is a variant of the Mil-17.

This is a Mil-171 with the same large freight door on the right (picture source). It looks very similar to a Mil-8 from which it is derived but can be distinguished by the opposite placement of the tail rotor (which is on the right side in case of the Mil-8).
Since this is (together with the Mil-8) the most common helicopter worldwide, it comes in lots of variants. This one here could actually be a Mil-171Sh, as Wikipedia says:

Actual model numbers vary by builder, engine type, and other options. As an example, the sixteen new Ulan-Ude-built machines delivered to the Czech Air Force in 2005 with -VM model engines were designated as Mi-171Sh, a development of the Mi-8AMTSh. Modifications include a new large door on the right side, improved Czech-built APU, and Kevlar armor plates around the cockpit area and engines.

The large door on the right side is very prominent in your picture. Also, the engine exhausts of the Mil-17 are covered by large boxes in case of the Mil-171 which dilute the exhaust gasses and make them less prominent for heat-seeking missiles. It is hard to see in the Google picture, but it seems that helicopter also has those boxes installed. Another change is the rear ramp of the Mil-171 which replaced the clamshell doors on the Mil-8 and -17. It seems the helicopter in the Google picture also has this rear ramp, visible by the tapered shape of the rear fuselage.
Wikipedia also knows that

The US was reportedly considering adding the helicopter to the US military for special forces use in order to obscure troop movements. The US has used some Mi-8s and Mi-17s for training, and has purchased units for allies in Iraq, Afghanistan and Pakistan.

The Mil-8 and -17 come in countless variations, that's why I show two pictures. It is very hard to find a good one of the right side; most on the Net are showing the left one.


text:
Do fighter jets have windshield wipers?
I was wondering if fighter jets do have windshield wipers for the rain. Other airplanes do. I can imagine that you don't need them because of their speed but I wasn't able to find some clear information about this. Maybe they use a different kind of windshield wiper, so I'm curious about what they have and use for rainy circumstances for their view.

https://www.youtube.com/watch?v=sZIjIr0Dl30

Makes me wonder why you would need to have good visibility during takeoff. Maybe to detect a vehicle or animal?

No modern US fighter jets are equipped with windshield wipers.  At faster speeds they aren't needed as moderate rain simply blows off.
Heavy rain at slower approach speeds will sometimes present a problem however...
The EA-6B, (while not technically a "fighter" by USN vernacular, it was tactical jet flying at similar speeds...)  used bleed air from a diffuser at the base of the windscreen to blow heavy rain off during approach to improve visibility.  It was airspeed and time limited to avoid excessively heating the windscreen, but was effective enough.
I imagine that most fighters have a similar system.

The F-4 had a similar system. It was hot, high pressure air from the 17th stage of the compressor. There was a warning in the dash one to not leave it running after landing, lest it crack the windshield.  Couldn't have windshield wipers, they would just rip right off at high indicated or calibrated airspeeds.

Interestingly enough, naval ships have a rotating glass (plexiglass?) disk mounted on the plate glass window on the bridge, that "slings" the rain off centrifugally. Navy dudes have a special name for this device, that escapes me.

@CharlesBretana, I'm sure I've heard it called by some other (manufacturer?) name, but Wikipedia knows it as clear view screen.  I wouldn't want to design one to survive fighter speeds, though!  Not even if it's prevented from operating above approach speed.

They're often called Kent Screens

Fighters or other airplanes without special provisions like boundary layer blowers or wiper systems, that fly in rain a lot, can/will apply water-beading coatings like "Rain-X" or an equivalent product to windshields, which does a good job of providing a decent view even at low speeds because the coating breaks up the water into extremely fine beads.
It's not a bad idea to carry a little bottle of Rain-X in your car. If your wipers fail, applying it can allow you to continue driving in rain in a pinch.

At highway speeds Rain-X works wonders in light rain, so should do fine on a fighter, even landing, in mist or light rain. In heavy rain or lower speeds wipers help greatly.

The problem with Rain-X is when the wipers are on the blade ends up leaving a layer of microbead fog that follows the blade's movement like a radar display shadow. Really annoying. When I've applied it I've generally avoided using the wipers at all. Some corporate jets and other have windshields with an acrylic outer layer and you want to avoid wiper use. RainX is an ideal alternative.

I love Rain-X, it just isn't a complete cure-all. Very common in the Pacific Northwest because it is quite good, but not perfect.

@JonCuster Yes besides the fogging problem when the wipers are on, I think you can get to an intensity that only wipers can cope with.

No, because they do not need them.
This video, named See Why Jets Don't Need Windshield Wipers shows an in-cockpit view of an American jet taking off from an aircraft carrier.
You can see that prior to takeoff the canopy is covered in rain drops:

But due to the acceleration and speed of they are all gone by the time the aircraft is airborne.

A cat launch is definitely different than a standard takeoff roll from a land based runway. Plus, there's always the taxiing portion (even on a carrier) where wind is likely not sufficient to blow rain off a window.

@FreeMan Cat launch? Are you referring to the experiemnts where jet pilots took cats into teh cockpit to see how they behave when launched into low gravity? The cats thought that there experiments were zero fun...and made sure that they were even less fun for the pilots. You know, when your view isn't obscurbed by water drops on the windshield but from blood drops.

@Klaws Catapulted launch! Silly!

Unnecessary Use Of Cat.

Always nice to see Growler Jams.


text:
What airfoil is used on the MQ-1B Predator's wing?
There are lot of UAV's in todays world to be re worked on. The General Atomics series of UCAVs is quite remarkable. I have selected MQ-1B Predator UAV, for an geometric analysis project(undergraduate).
Though the wing dimensions including root and tip chord's length are found at https://mq-1predator.weebly.com/design-and-specifications.html and the rest performance specifications for it is available at https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104469/mq-1b-predator/.
Still it isn't mentioned anywhere at websites and in factsheet too, about its "Airfoil profile".
I have been trying to figure it out.
Can anyone please help me out to ascertain MQ-1B's airfoil profile?

Look at this table: https://pdfhall.com/the-incomplete-guide-to-airfoil-usage-ulm_5b6dd1b0097c47783f8b45b8.html

The MQ-1B uses three different airfoils: Drela GW-19, GW-25 and GW-27, created by Dr. Mark Drela (one of the creators of the XFOIL software) and proprietary to General Atomics.

The airfoils used on the MQ-1B (Drela GW-19, GW-25, GW-27, created by Dr. Mark Drela) are proprietary material of General Atomics. Dr. Drela personally stated on a hobbyist remote-control drone forum that a scale model should use an SD7032 wing (similar shape to a NACA 3510), while the full-scale MQ-1B airfoils "...have LOTS of top surface camber."

"Fixed-Wing UAV Airframe Design and Validation", Bachelor's Thesis of Timothy Brown, University of Queensland

Heh, I must have been wearing my glasses sideways. :)


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Tracking freighter and charter planes between two specified airports
Is there a way to find the historical data of the freighter and charter planes between two airports

Welcome to aviation.SE! Does this question help?

How historical? With subscription flightradar24 offers flight history up to a year.

If you know the tail numbers of the aircraft, you can go to FlightAware.Com and request flight history there. Even if they have not filed flight plans (highly unlikely if they are commercial flights), if they are equipped with ADS-B the odds are high they will be picked up by the system at some point during their flight.


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Airplane Parachute
I want to ask two questions.

Why don't they have parachutes on a passenger airplane?

Could it be possible to have a parachute designed for their airplane? Like a big parachute that can safe the crash of an airplane if it stops working.

Generally because they have extra engines that are extremely reliable.  Parachutes do exist for single engine planes, but let's not forget gliding on the wing:  a far more efficient way to make use of available altitude.

Simply put, the weight of such a system alone is enough to make it not feasible.
Rescue chutes work satisfactorily on smaller planes as they are, not surprisingly, quite light. For a passenger plane, the parachute should be (at least) an order of magnitude bigger i  relation to plane size. This is because if you double the mass, you quadruple the forces acting on the chute. In addition to the bigger mass of the passenger plane, the speed is also vastly higher. Again: double the speed = quadruple the energy.
The structures needed to take the shockloads of the chute opening would be very, very heavy, making the situation even worse.
And... even with a rescue chute, the "landing" is anything but soft. A lighter small plane will survive that relatively intact, but a large plane would most probably not. If you try to lower the descend speed with a larger chute (or multiple chutes), you again get loads of extra weight.
...and... then there's the buildingin + maintenance cost. The system itself would be expensive to manufacture, install and maintain.
So: while it would be technically possible, economically it is not. You would end up with very poor payload capacity, and unreasonably high ticket prices.

Simply put, planes are designed to not crash. Anything kind of safety measure you add to a plane will come with some opportunity cost - instead of that particular safety measure, you could have spent that money on something else. Overall, it's more cost effective to implement safety measures that prevent the plane from crashing in the first place, rather than trying to mitigate the consequences.
A plane-sized parachute will add weight, complexity, maintenance, etc. to every single plane that has one, and it will only be used in an extremely small number of cases. You'd be better off spending that money on improved pilot training, more frequent maintenance schedules, or any number of things that reduce the likelihood of a crash. The best way to survive a plane crash is to not crash in the first place.


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How does a U.S. military air traffic controller become a civilian air traffic controller?
If a person is working as a United States military air traffic controller and then they get discharged, do they have to go through additional training and tests to work as a United States civilian air traffic controller? or do they just get hired, without any additional training and tests?

Wasabi's answer is not correct, or at least not fully correct. You actually ask two questions: does a military controller need to take additional tests and training to get hired, and do they need additional training to work as a civilian controller. The answers, respectively, are "no" and "yes."
The hiring practices change every so often, but here's how it is now:
"Off-the-street" FAA controllers receive training at the FAA Academy in Oklahoma City. This training starts with Air Traffic Basics and continues to Initial Tower Cab (for Terminal-track new hires) or Initial Enroute (for Enroute hires). New hires do not go directly to standalone TRACONs anymore. People who graduated schools in the Collegiate Training Initiative do not have to attend Basics but do attend Initial.
In order to get to Basics, new hires must take the ATSA aptitude test, as well as undergo medical and security investigations.
After graduating the Academy, new trainees are sent to their field facilities and go through classroom and simulator training before eventually progressing to On-The-Job instruction (plugged in working live traffic alongside a trainer who retains ultimate responsibility for the control position). Any controller, even one who has been previously certified at an FAA facility, must go through this facility-specific classroom/sim/OJT progression any time they transfer to a new facility.

Prior-experience new hires (who mostly come from the military) may elect to go through the off-the-street hiring process if there is a bid open at the time they are discharged. But usually they apply though a separate bid that is only open to prior-experience controllers. This bid allows them to be placed directly at a facility that should, in theory, correspond to the type and level of their prior experience; this is almost always a Terminal facility (tower, up/down, or TRACON) but an Enroute facility may be offered very rarely.
If necessary these new hires may be sent to the Academy for training, for example if they only worked radar before but were assigned a tower facility, but for the most part they enter the training process at their new facility immediately. This process is not waived just because they have previous experience. They do benefit by not having to take and pass the ATSA aptitude test, however.

As far as "tests" go, in the FAA, there are annual or biennial "refresher" simulator problems and "skills evaluations" where a supervisor does a limited checkride with the controller to ensure they don't need additional training in any area. But this is based on when the controller certified at their facility and has nothing to do with any tests they might have done in the military.

Good answer. In the Center environment, military ATC time is useful for phraseology and gives you a boost in aptitude, but the training will be the same as a new hire. At Denver ARTCC, that's academics, the Training and Testing Lab (TTL - my world), certifying on Interphones (about a year), back to the TTL (you, again?), and finally, certifying on radar (about a year). You will have spent approximately 3 years checking out in an ARTCC, after you walk in the door. C'mon over!

No. A US military air traffic controller does not need additional testing nor training to become a civilian air traffic controller. This is because the testing and training for military Air traffic controllers follow the same basics as civilian air traffic controller testing and training, but with additional requirements, training, and testing to fit the needs of the military. Any test given for a civilian air traffic controller is also taken by a military air traffic controller. An air traffic controller needs to retake tests each year, whether they are a civilian or a military air traffic controller. So as long as the discharged military air traffic controller applies to become a civilian air traffic controller within 1 year of his/her last test, he/she can become an air traffic controller without any additional testing or training whatsoever. But, once a year has past since his/her last test, they must retake the tests. But when they retake tests, they only need to retake civilian air traffic controller tests, and not military air traffic controller tests. This is because they aren't working as a military air traffic controller anymore.

If a Military Air Traffic Controller is looking to be hired as a civilian air traffic controller because they were discharged from the military due to being 31 years or older; they can apply to be a civilian air traffic controller even though they are 31 years are older, because of FAA's Phoenix 20 program. This program allows them to work past the age of 31, and it can also allow them to continue working for the military before moving to the FAA to continue air traffic control as a civilian air traffic controller, according to https://www.govinfo.gov/content/pkg/GAOREPORTS-GAO-02-591/html/GAOREPORTS-GAO-02-591.htm
So, a Military Air traffic controller does not need to retake tests before become a civilian air traffic controller unless they have not retaken tests in 1 year since the previous test retake.


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What is the general operating temperature of Free Piston Turbine Engines?
The turbine in turbine engines can face temperatures from the combustion chamber up to 1700ºC, but I can't find any information on the operational temperature of free piston turbine engines.
I'm interested on the subject because if free piston engines don't use the same absurd amounts of heat turbine engines normally use, then more conventional materials could be used for the turbine instead of super alloys.

For a 20 kW engine with a 20 L tank and a bore of about 10 cm, the tank's temperature should be about 300 K (isothermal) to 400 K (adiabatic, more practically), says p. 11 of an analysis by Sandia Labs, "Optimizing the Scavenging System for a Two-Stroke Cycle, Free Piston Engine for
High Efficiency and Low Emissions: A Computational Approach," by Goldsborough and Van Blarigan, SAE Trans. 112(3): J. Engines, pp. 1-20.
400 K is 125 ºC, comfortably cool.

Newcastle U. investigated (unpaywalled) cylinder wall temperatures from 370 K to 435 K (p. 383, top) and a modified "low heat rejection design" with wall temperatures up to "50 per cent" higher (p. 384), thus at most 650 K.
(Mikalsen & Roskilly, "The fuel efficiency and exhaust gas emissions of a low heat rejection free-piston diesel engine," Proc. IMechE (A): J. Power and Energy 223:379-384.)
650 K is 375 ºC, still cool enough for non-exotic piston materials, despite the in-cylinder gas temperature ranging from 400 K to 1800 K through a piston stroke (p. 383, Fig. 4).
But Fig. 8 shows that the steady-state exhaust gas temperature is 1100 K to 1140 K (870 ºC), so the turbine itself must be made of sterner stuff.

Any sort of heat cycle engine (Brayton - gas turbine, Otto - gasoline engine, Diesel, Carnot, etc) will have peak efficiency and power output with a higher peak temperature.
Consequently, all of these kinds of engines push towards higher temperature materials.
Note that modern piston engines require hardened valve seats (particularly exhaust valve seats) in order to handle higher temperatures -- as compared to early piston engines that could get away with soft valve seats (typically cast iron).
Higher temperatures is one of the most fundamental ways to make an engine better.

This is the key - engines are designed to run at the highest temperature they can handle because it improves efficiency. Turbines are only hotter than piston engines because it's possible to build turbine blades to be more heat-resistant than pistons. Any sort of device that reduces the input temperature of the turbine will also reduce efficiency.

@RobinBennett Counter example on [Water Injection](https://en.wikipedia.org/wiki/Water_injection_(engine)) In reciprocating engines, the air pressure at sea level has too much oxygen, which means you have to run the engine lean to prevent overheating. This reduces efficiency as the combustion is detonating early. Injecting water cools the engine, making early detonation less likely to happen, which increases efficiency

This does not answer the question. I don't think "higher" is what was desired.

The question has been edited since my answer was posted -- it does seem a bit of a moving target.  My point is that adding a lot of heat is the point of an engine -- that is how you get high specific power (a necessity for flight) and high temperatures are also a good thing - they're how you get high efficiency.  I.e. There is nothing about free turbines that would push them to use lower temperature materials.  If there were, then optimizing that design would drive the temperatures back up.


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How were bullets fired through the propeller in the Focke Wulf 190?
In WWII there was a plane called the Focke-Wulf Fw 190. It was designed by an engineer called Kurt Tank.
How is it possible that the Fw 190 fires through the propeller from 4 different places as you can see in the picture below? There are two machine guns right in front of the pilot, and one at either side on the wing, close to the body of the plane.

There were early planes where they simply didn't bother with synchronization, and just "hoped for the best" (https://en.wikipedia.org/wiki/Synchronization_gear#Unsynchronized_guns_and_the_.22deflector_wedge.22_concept)

The Internet is incredible. I found a PDF of the manual for the armament of the Fw-190 online here. In it, the components are described sufficiently to be sure that synchronization in the FW-190 was achieved electrically.

General arrangement of the armament in the Fw-190 (picture source). The pipes running to the wing cannons feed hot air from the engine to the ammunition box to keep the temperature there above -35°.

Detail view of the Sicherungs- und Verteilerkasten SVK-2 (circuit breaker and distribution box) for the MG 151/20 in the wing root (picture source). Clearly, the weapon was electrically controlled.
The Wikipedia page on gun synchronization already mentions that with firing rates above 400 rounds/minute, mechanical synchronization became unreliable, and at the end of WW I, the first electrical gun synchronization by Siemens was used in LVG attack planes, and Aviatik employed their own system. The much higher firing rate of WW II guns required electrical synchronization, and only some Russian fighters continued to use mechanical synchronization into and even beyond WW II.

Very good and definitely specific to the question! I hope that the asker will consider accepting this answer since this is actually using different technology than the early mechanical implementation.

Note: See Peter Kämpf's answer for specifically how the Fw 190 Achieved this Electronically
This answer is specific to how this was achieved via mechanical means in earlier aircraft and not specific to the Fw 190.
It's called a "Synchronization Gear" and it allows the gun to fire only when the blade is not in front of the barrel.

Source: Kaiserliches Patentampt (Imperial German patent Office) / Franz Schneider - Patentschrift No. 276396, 1913 First published in Flugsport" (1914) and in many places since, Public Domain,

[From Wikipedia] Interestingly, the linkage between the propeller and the gun is achieved with a spinning drive shaft rather than a reciprocating rod. The impulses needed to operate the trigger, or in this case to prevent the trigger from operating, were produced by a cam wheel with two lobes at 180° apart situated at the gun itself, since the gun is interrupted by both blades of the propeller.

These have been around since before 1920, long before the aircraft you mention in your original post.
The one on the Fokker (not Focke-Wulff, but still German) differs a little bit from the patent image above:

Source: By Gsl - Version with English text of Image:Interrupter_gear_diagram.png, Public Domain
But not significantly, the basic idea is that the trigger mechanism follows a cam lobe which is tied to the propeller shaft. When the cam lobe spins, the trigger is allowed to fire the gun only when the propeller isn't "in the way".
See Wikipedia Article on the Synchronization Gear for more information.

Thanks for the explanation with the pictures included, what puzzles me in the FW-190 pictured in the question, is the fact that it had 4 machine guns, 2 of them on each wing - that would have to be in sync with the blades.

Only the inner ones would have to be synchronized, and it would just mean another rod on the cam wheel to feed the other gun. The cam wheel on the FW190 probably had multiple lobes for the 3 bladed propeller.

Worth noting that this is essentially the same type of synchronization mechanism that does things like lifting engine valves and firing spark plugs at the right time.

Fokker (not Focke-Wulff, but still German) uhm, Fokker was Dutch?

"The company operated under several different names, starting out in 1912 in Schwerin, Germany, moving to the Netherlands in 1919" So I'm not entirely wrong :) I'll change it though... On second thought I won't change it, at the time the above device was created, Fokker was still German.

Wierdly, in the case of this aircraft it looks like the guns could easily have been mounted out of the sweep of the propeller, removing the need for synchronization. I wonder what engineering constraint meant it made sense to have synchronized firing: wing thickness or width, vibrational stability, wing strength, position of flaps...

@DanSheppard If you look at the cutaway drawing of the gun arrangement you can see that the inner guns are larger caliber than the outer guns. The outer guns have a much smaller magazine where the inner guns have a large magazine located inside the main fuselage.

I have to look it up, but I am almost sure the Fw-190 used electric synchronization. The mechanical way was first, but Focke-Wulff was far ahead of all others on the way to the all-electric aircraft. Just look at the cockpit and count the number of circuit breakers in a Fw-190.

Fokker, the designer was german, and designed aircraft for the germans in WW1, at the end of ww1, he moved to holland.

@JourneymanGeek Anthony Fokker was Dutch. He designed and built his first aircraft in Germany and moved his business to the Netherlands after WW1.

@RonBeyer apparently not smaller calibre from the parent wikipedia page (and the English version) - all 20mm, though the 7.92s on top of the engine were also synchronised

Vaguely relevant.

@marcellomiorelli consider reviewing the newer answers because one directly addresses this model aircraft.

Since WWI, there was a device called a Synchronisation Gear which staggered the firing of the gun so that it would not hit the propeller of the plane.

I can't seem to locate the reference but the synchronizing gear was not at first used with the forward firing gun. The inventor of the forward firing gun had steel plates mounted to his propellers to deflect the occasional round that might hit the prop. This was satisfactory right up until he got his prop shot off. That's when the synchronizing systems were sought out.

Before they put deflector plates on they just fired the gun and "hoped" it missed the prop. Usually they would wrap the prop in a fiber tape that helped keep the prop together when inevitably hit by the bullets. Deflector plates came after "hope for the best".

@RonBeyer -- old topic but-- Roland Garros was the French pilot who achieved several victories with the "deflector plate" arrangement.  I've never come across any mention of a pilot who intentionally fired a machine gun through the prop with no deflector plates and no sychronization, though pilots certainly had experimented  with guns firing diagonally sideways and forward in a way that missed the prop, and guns mounted on top of the top wing that missed the prop arc.  Fokker had a synchronizer gear already under development before Garros's plane was captured and examined by the German side.

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What are the driving factors for performing a steep approach
What are the factors a pilot needs to consider before preparing for the steep approach?
How is steep approach combined with auto land feature.

This is a very broad question. Most aircraft require no certification for performing a steep approach. Airport requirements and pilot considerations vary widely with the situation. What industry sector are you considering in your question?

Okay I am mostly concerned from the aircraft perspective. When does pilot go for steep approach. What 'other' things need to be considered before engaging steep.

Usually a steep approach means they are avoiding an obstacle or have been asked by ATC to "make it short". A steep approach ends in a normal landing, if you are hitting the ground any harder than you do normally then you are performing the technique wrong. Speed can be managed in the approach so you are steep, but not fast, and it ends in a flare/touchdown just like any other landing. There are no certification requirements, but some aircraft are prohibited from slips or slips in certain configurations (like with full flaps).

Related: http://aviation.stackexchange.com/questions/21956/what-is-the-requirement-of-a-higher-glidepath-approach-angle-and-is-this-a-fligh

@JonathanWalters in the US perhaps - in the EU, there are specific requirements for aircraft to perform a steep approach requiring certification from the EASA

Edited the question to include Jeppesen chart of London UK

On ILS if you're coming in steeper than the glide slope you have to be careful not pick up a  false glide slope

Somewhat related tactical penetration descent

How is auto-land combined with steep approach?

The three questions are rather loosely related, which is bad format for this site. Voting to close as too broad.

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Are direct law command gains monitored for correctness when flight control computer is in normal mode?
This question is specific to Bombardier C-Series aircraft which  has three modes: Flight control computer normal mode, FCC Direct mode and REU direct mode:
(I am not sure if other aircraft have an intermediate mode before switching to alternate law)
Control law gains are computed for both FCC normal and FCC direct mode even if the computer is in normal mode. Direct mode commands are outputted when the switch happens from normal to direct.
Fly By Wire Flight control computer switches from normal law to alternative law under certain conditions (when minimum required sensor set is lost for instance).
So I assume the control laws are also switched from normal to direct.
Are the direct mode control gains computed and monitored when the flight control system is under normal law?

When the system is in normal law, it is in normal law, not direct law, so what do you think it should be doing with direct mode control gain?

There is nothing to compute on direct mode control gains. In direct mode, the output equals the input. And, somewhat notably, with centred stick the both normal and direct law outputs are zero, because normal law keeps the aircraft trimmed for its current speed, so unless the stick is off centre (which is rare), switch to direct law won't actually move the surfaces anyway.

Bombardier aircraft has one more intermediate mode called Flight Control Computer Direct Mode (before switching to REU* direct mode, where pilot inputs are directly translated into surface movements). This is a mode with reduced functionality but still FBW system computes the gains. Hence we have two control laws: Normal and Direct mode control laws. Is it not the case usually?
*REU - Remote electronics unit

You may want to edit your question to specify that you're specifically interested in the Bombardier FBW systems, then, to help reduce confusion.

@user2927392, you tagged the question “airbus”, so I am talking about the Airbus modes. Bombardier control modes, and their implementation, are different from Airbus ones (and I know absolutely nothing about them; I only read up on the Airbus ones).

My mistake. I assumed that Bombardier design is inherited from airbus.


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How far could the Airbus A321XLR actually fly commercially?
Airbus states

It will offer even more range – up to 4,700 nm (8,700 km) – in a comfortable 2-class layout

There is an animation which contains this:

And that is 4735 miles. So now I am intensely curious what's actually possible.

The question is too general, what do you mean by "fly commercially"? Any airplane can fly farther with no payload than it can with a large payload, but the payload at which the flight is commercially viable will depend on the costs and revenues for that specific flight. There may also be difficult to quantify business factors such as the marketing benefit of holding a best in class title, or customer loyalty derived from more profitable routes that connect to this long route.

Well, I mean, not a test flight but something they could actually market and sell.

Airbus is quoting the ranges in nautical miles (nm) which is typical for aircraft. The Great Circle Mapper you linked is using statute miles, which are shorter. If you switch it to be in nautical miles, you get 4115 nm, which is well within the quoted range.

facepalm SI for the win, thanks!


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Can a single seater airplane fly with 50 lbs of thrust
An airplane with 10 sq meters of wing five meters fuselage and including one person. can it fly with 50 lbs of thrust? And the max weight  is 400 lbs

If you meant something more along the lines of "Is it possible to design a single seater airplane with 10 square meters of wing w/ fuselage 5 meters long that can fly on 50 pounds of thrust", as opposed to "pick some plane w/ these parameters, can it fly on 50 pounds of thrust"-- you might want to edit to clarify--

A key thing you need to provide is the ratio of L/D, which is also equivalent to the ratio of Cl/Cd, where Cl and Cd are the lift and drag coefficients.
Thrust required for level flight = D/L ratio * Weight.
Without knowing more information, including L/D ratio and Weight, the answer to your question can only be "maybe".
If the L/D ratio is 10:1 or better and the total weight is 500 pounds, then the answer is "yes".  Increase the weight or decrease the L/D ratio, without changing the other variables to compensate, and the answer becomes "no".
Also, naturally, we have to know the thrust available at the airspeed that we are actually going to fly at, which may, or may not, have been what you were referencing-- (I assumed it was, in the preceding paragraph.)
Edit: since you've now provided the total max weight at 400 pounds, the answer is "yes, as long as the L/D ratio is at least 8:1, and the full 50 pounds of thrust is actually available at the airspeed at which you are flying."  An 8:1 L/D ratio is certainly doable.  Of course there would be no excess margin to allow for climbing, if the thrust were exactly equal to drag (50 pounds in the case of an 8:1 L/D ratio) and no more.  If you can get the L/D up to, say, 15:1, the performance will be a lot better.  (I'll leave the actual calculation for achievable climb angle in that case up to you, but all the required information is present here.)

Realistically it’s not much fun to fly an aircraft that can’t climb at 200ft/min at the very least.  If you want to do it once just because you can then go for it.  Compare with a paramotor that can fly with (usually) at least 250N thrust, has a weight of around 220-250lb and a wing area of about 25sqm.  Aerodynamics are generally awful and airspeed is quite low (20kts).  To achieve the smaller wing area you’d want to fly quite a lot faster and so you’d want a lower-drag design, which would be quite easy to achieve - getting rid of the 2km of lines would be a good start.

@Frog: But in the case of a paramotor (or paraglider) the low airspeed is a feature that is very much desired. Aerodynamics aren't really all that important at low speeds.

@ymb1 -- um, yes, obviously-- good catch

@jamesqf Quite so; with a similar engine I’m examining what characteristics a more conventional fixed-wing aircraft would need